The present invention relates to a digital mobile communication system and a timing design method between various subsystems, and more particularly, to a digital mobile communication system wherein a master clock of a mobile communication system for offering audio or data service using a code division multiple access (CDMA) is set as a global positioning system (GPS) clock provided in a GPS and the interface and timing between various subsystems using the GPS clock and an exchanger are redesigned to achieve an exact timing schedule, and a timing design method between various subsystems.
In general, all existing exchangers and various subsystems connected thereto adopt a frequency synchronizing method to match a timing synchronization because they simply transmit a message (information), without any need for another synchronizing methods.
However, the existing communication methods are changing from cable methods to wireless ones, and from analog methods to digital ones.
Accordingly, there have been developing an exchanger, a control station and a base station using the CDMA method. The control station for a CDMA used for mobile communication requires a timing synchronizing method for determining concurrently input signals from two base stations, i.e., determining whether the signals are input concurrently, when the respective subscribers' terminals are moved during transmission/reception (a hand-off state).
The mobile communication system using the exchanger for CDMA adopts a timing sync method as well as a frequency synchronizing method in the timing synchronizing method between the control station and various subsystems connected thereto.
Here, the frequency synchronization is a basic function for preventing data loss or error in all the digital systems, for implementing its function by defining a master clock and extracting its own clock using a slave mode in the respective subsystems to then function in accordance with the clock. The time synchronization is used for transmitting frames from two base stations to one mobile terminal during a soft hand-off state, transmitting frames from two base stations to one base station controller to sort frames in the base station controller having received the frames and for minimizing a round trip delay.